如何在swift ui的导航视图中的大标题下添加字幕？

struct ContentView: View {
    var body: some View {
        NavigationView {
            Text("Main Content")
                .navigationTitle("Title")
                .navigationBarTitleDisplayMode(.large)
                .toolbar {
                    ToolbarItem(placement: .principal) {
                        VStack {
                            Text("Subtitle")
                                .font(.subheadline)
                                .foregroundColor(.secondary)
                        }
                    }
                }
        }
    }
}